1. Field of the Invention
The present invention relates to an insulated wire using a specific polyimide as the insulator and a process for the production of the insulated wire.
2. Prior Art of the Invention
Recent years have seen dramatic developments in the electrical and electronic industry. In particular, apparatus used in the industry have become smaller and lighter in weight, and hence, more excellent heat resistance is desired for machine parts and insulating materials.
Aromatic polyimide has excellent mechanical properties, solvent resistance and electrical insulative properties in addition to the highest thermal resistance among organic polymers. Examples of the aromatic polyimide are a polyimide prepared from bis(4-aminophenyl) ether and pyromellitic dianhydride (KAPTON,VESPEL; a product of E.I. Du Pont de Nemours & Co.) and a polyimide prepared from bis(4-aminophenyl) ether and 3,3',4,4'-biphenyltetracarboxylic dianhydride (UBILEX; a product of Ube Industries Co.).
Since heat-melting is difficult in these polyimides, it is difficult to produce an insulated wire by a melt-extrusion process.